The use of a power takeoff device (herein referred to by its art recognized abbreviation “PTO”) in association with truck or other vehicle (or stationary engine) transmissions is well-known. Generally speaking, such PTO's often include an input gear, an output gear and a mechanism f or engaging the input gear with the output gear so as to rotate the output shaft of the PTO to power an auxiliary device, with or without the use of an intervening hydraulic pump, to perform useful work when desired. The mechanism also provides a means for disengaging these two gears.
The input gear of the PTO is, in certain popular designs, constantly engaged when installed on the vehicle's transmission with the appropriate gear in the transmission and is, thus, always turning whenever that gear in the vehicle's transmission is turning. A clutch mechanism is then conventionally provided between this input gear of the PTO and the output gear, enabling selective rotation of the output shaft of the PTO (associated with the output gear). When this output shaft is rotated, useful auxiliary work can be performed by the vehicle in a known, conventional fashion, for example, by connecting the output shaft to a hydraulic fluid pump having a fluid reservoir system, which hydraulic fluid under pump pressure generated by the turning PTO output shaft, in turn, is used to operate auxiliary equipment. Just a few examples of such auxiliary equipment are garbage compacting bodies, dump bed bodies (a/k/a, “dump trucks”), garbage trucks or trailers, winches, post hole diggers, and the like.
An example of such a PTO with an appropriate and effective engage/disengage clutch mechanism is disclosed in my commonly owned U.S. Pat. No. 5,542,306, issued Aug. 6, 1996. An embodiment thereof is illustrated herein in FIG. 1 (prior art). While certain differences exist between FIG. 1 and the embodiment in U.S. Pat. No. 5,542,306, they are each generally representative of a popular commercial clutch operated PTO upon which this invention now improves.
With specific reference, in this respect, to FIG. 1 (prior art) and as more fully described in the aforesaid U.S. Pat. No. 5,542,306, there is disclosed a power takeoff 27 having a housing 27A, which conventionally includes a customer/input gear 29. Input gear 29 is coupled to input ratio gear 39. In practice, ratio gear 39 is usually provided with a specific gear ratio applicable to the particular truck's (or other type vehicle's or stationary apparatus') transmission needs and the selected torque output desired. Cone bearings 31 are also provided. Gear ratios from 5-8 are conventional. Also, conventionally provided in this former PTO is power takeoff output shaft 33 which is provided with a stub end 33A that connects power takeoff 27 via key 34 (e.g., a woodruff key) to an extension shaft (not shown for convenience) which, in turn, conventionally leads to a hydraulic fluid pump operated by rotation of this shaft. Alternatively, stub end 33A of shaft 33 may be directly connected to a hydraulic pump or to any auxiliary equipment directly operable by the shaft, thereby to provide, for example, when it is directly connected to a pump, in a known manner, a “direct mount” PTO/pump configuration. In either this “direct mount” configuration, or in the “remote mount” configuration (see FIG. 3, discussed below), unwanted rotation of shaft 330 may be prevented in the invention herein, in the same way, as described in the aforesaid U.S. Pat. No. 5,542,306 by providing a drag brake mechanism which constantly applies a sufficient braking force to prevent shaft rotation when the clutch discs operating means is operated to disengage the 5 discs. The drag brake, however, is designed to apply an insufficient force so that it is overcome when the discs are engaged, thereby allowing the shaft to rotate. This feature, fully disclosed in the aforesaid patent, is not illustrated herein for convenience, but may be used in o combination with this invention herein below described, as an option, as will be evident to one skilled in the art.
Associated with the operation of gear means 29 and shaft 33, in FIG. 1, is a connect, disconnect clutch mechanism. Such a mechanism includes piston 35 and clutch S hub 37. To clutch hub 37 there is attached a plurality of friction discs 37A (shown in FIG. 1). Piston 35 and clutch hub 37 are attached to shaft 33 so as to rotate whenever shaft 33 rotates. Hub 37 is non-movably attached to shaft 33, while piston 35 is slidably attached thereto. Spring 36 is located between hub 37 and piston 35 and normally biases piston 35 away from rearward most friction disc 37A-1 in the friction disc stack 37A.
Constantly rotating with the rotating gears of the truck's transmission and, thus, not permanently attached or connected to shaft 33, are customer/input gear means 29, input ratio gear means 39 and output gear means 41 (including hub 43). This sub-assembly is allowed to rotate about shaft 33 on needle roller bearing 42 whenever the PTO is engaged with the rotating gears of the truck's transmission, even when the clutch mechanism has successfully achieved its disengage position so that shaft 33 is not rotating. Output gear means 41 has attached thereto, i.e., to hub 43, a plurality of spacer discs 45 located so as to be interspersed between friction discs 37A. Spacer discs 45, of course, rotate whenever the aforesaid sub-assembly rotates. Properly operating, friction discs 37A, attached to clutch hub 37, do not rotate when the clutch mechanism is in its disengaged position (as shown). Thus, rotating spacer discs 45 merely rotate between, their respective friction discs 37A until compressed into contact with friction discs 37A by piston 35 to cause, via friction in the stack, all discs to rotate together. This, then, enables selective rotation of shaft 33.
As alluded to above, to prevent unwanted rotation, such as by incomplete disengagement due to various possibilities the aforesaid U.S. Patent No. 5,542,306 provides a unique drag brake mechanism for preventing such unwanted rotation. Such a drag brake mechanism as disclosed in this aforesaid patent (No. 5,542,306) may also be optionally provided in he practice of the subject invention for the same purpose of preventing unwanted rotation.
While the aforesaid PTO disclosed in the ’306 patent and/or as shown in slightly different form in FIG. 1 nor art) proved in actual practice to be quite advantageous, it was found that further improvement was desirable. In this respect and with further reference to FIG. 1, it was found in practice that the snap rings 101 and 103 eventually fatigued to breakage when employed on a vehicle (or in other uses) which required exceptionally high shift cycle applications. The use of heavy duty snap rings to overcome this drawback, proved to offer only marginal improvement in the useful life of these rings. This was due to the fact that snap rings 101 and 103 inherently functioned to contain the clutch pack friction forces. This, in turn, created not only the need for heavy duty snap rings, but gave rise to a need in high shift operational applications for another solution which would allow for the use of regular duty snap rings without incurring the frequency of the fatigue problem referenced above, at times even with heavy duty snap rings.
It is a purpose of this invention to fulfill this and other needs in the art which will become more apparent to those skilled in the art once given the following disclosure.